The present invention generally relates to wire cutting apparatus and more particularly relates to the drive mechanics and control mechanisms for controlling the operation of a wire cutting apparatus.
Wire manufacturers typically coil wire, usually of a predetermined number of lineal feet, onto relatively large spools or into coils. Before the wire is used or shipped to market, it is often necessary to cut the wire from the coil into shorter segments also of a predetermined length. In order to transform the wire from the curvilinear shape it assumes as a result of being coiled, a wire straightening apparatus is often provided to straighten the wire and alleviate any radial forces tending to bend the wire. Straightened wire can then be feed through a wire cutting apparatus along a predetermined path to make the aforementioned segments of relatively short length.
In order to automate and optimize the cutting process, a release mechanism that includes a proximity sensor is provided downstream of the cutting apparatus to sense the presence of wire and signal the cutting apparatus to make each cut at the appropriate time when the desired length of wire segment is reached. Such a release mechanism is disclosed in Yankaitis, U.S. patent application Ser. No. 08/868,908 assigned to Rockford Manufacturing Group, the entire disclosure of which is hereby incorporated by reference. The cutter is often a blade or shearing knife which oscillates up and down to partially or fully cut through the wire. A wiper is typically provided in conjunction with the cutting apparatus to break the wire segment away from the rest of the wire stock if necessary. Such a wiper mechanism is disclosed in Burns, U.S. Pat. No. 5,850,773 assigned to Rockford Manufacturing Group, the entire disclosure of which is hereby incorporated by reference. This automation technology has significantly reduced labor and manufacturing costs and increased production rates.
To periodically cut wire each time the proximity sensor senses the desired length of wire, the prior art has typically provided a continuously rotating electric motor that has an output connected to the input of a one-revolution clutch/brake mechanism whose output acts to operate the cutter. The clutch/brake mechanism is normally disengaged and thus the clutch/brake mechanism output and the cutter are normally idle. When the wire advances to the desired and suitable length, the clutch/brake mechanism is automatically engaged and acts to operate the cutter to cut through the wire, at the end of which the clutch/brake mechanism is automatically disengaged. Typically the clutch/brake mechanism is engaged at a relatively high frequency on the order of about 2-3 times every second (depending upon the length of wire segments cut) to successively cut relatively short segments of wire from the wire stock.
While the clutch/brake mechanism provides adequate speed and achieves the advantages of automation, the clutch/brake mechanism is susceptible to reliability problems. In particular, frequent engagement and disengagement of the clutch/brake mechanism to successively cut wire segments results in short clutch/brake mechanism life. It may be necessary to replace the clutch/brake mechanism of a wire cutting apparatus on the order of several times a year, or even monthly, which in turn results in temporary shutdown of the cutting apparatus and costly and laborious replacement of the clutch/brake mechanism.
It is the main objective of the present invention to increase the reliability of a wire cutting apparatus and provide a more practical wire cutting apparatus.
In that regard, it is a specific objective to reduce the number of temporary breakdowns in a wire cutting apparatus caused by rapid deterioration of the clutch/brake mechanism.
It is another objective of the present invention to reduce the cost of providing and operating a wire cutting apparatus.
It is another related objective of the present invention to increase production rates of a wire cutting apparatus.
According to one aspect of the present invention, a wire cutting apparatus includes an electrical motor carried by the support having an output driving a cutter holder which holds the wire cutter. A first proximity sensor arranged in sensory communication with the wire cutter produces a signal indicating location of the wire cutter relative to the wire path. A second proximity sensor arranged downstream of the cutting station, produces a signal indicating presence of wire in proximity to the end of the predetermined wire path. A controller is responsive to the proximity sensors to control output to the electrical motor. The controller selectively generates a first electrical output to the motor to work the wire cutter into the predetermined wire path and a second electrical output to decelerate the motor and maintain the wire cutter adjacent to the wire path, thereby allowing wire to advance.
According to another aspect of the present invention, a wire cutting apparatus includes an electrical motor carried by the support having an output oscillating the cutter holder and therefore the wire cutter. The motor has run and stop modes for selectively oscillating or holding the cutter stationary. The motor is capable of oscillating the cutter at a first frequency during a continuous run mode of the motor. A proximity sensor is arranged downstream of the cutting station for producing an output signal indicating presence of wire in proximity to the end of the predetermined wire path. A controller selectively generates an output to the electrical motor in response to output signals from the proximity sensor. The controller continuously drives the electrical motor when a second frequency of the output signal from the proximity sensor is at least equal to or greater than the first frequency thereby to continuously cut wire segments without the necessity of stopping the motor. The controller intermittently switches the motor between run and stop modes when the second frequency is less than the first frequency, thereby allowing for longer segments of wire to advance.
According to another aspect of the present invention, a cutting apparatus comprises means that includes an electrical motor for actuating a cutting means up to a first maximum frequency to cut off successive leading end portions of wire. Sensing means arranged downstream of the cutting station produces output signals indicating presence of wire in proximity to the end of the predetermined wire path. Control means selectively generates an electrical output to the electrical motor in response to output signals of the sensing means. The control means continuously drives the electrical motor when a second frequency of the output signal from the sensing means is at least equal to or greater than the first maximum frequency and cyclically accelerates and decelerates the electrical motor when the second frequency is less than the first frequency.
Advantages of running the motor in a continuous run mode is that the life span of the motor and driven components may be increased and that the production rate may be increased by as much as about 100%. Advantages of cyclically accelerating and decelerating the motor is that wire can be advanced at a selected feed rate as desired, thereby allowing for longer segments of wire to be cut.
Other object and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.